1. Field of the Invention
The present invention relates to a storage system and a storage system management method.
2. Description of the Related Art
A storage system, for example, comprises at least one storage control device called a disk array subsystem and provides data storage service to a host computer (referred to hereinbelow as “host”). In a storage control device, a large number of disk drives can be arranged as an array, and a storage area based on RAID (Redundant Array of Independent Disks) can be created.
Furthermore, a backup site can be disposed in a location remote from the main site to cope with a large-area accident, this being known as the so-called disaster recovery system. A storage control device for backup is disposed in the backup site and a data group identical to that of the main site is stored in the this storage control device. As a result, even when the main site stops due to failure, or the like, the data processing service can be continued by the backup site. However, when a failure occurs in the only available backup site before the main site is recovered, the data processing service cannot be provided to the host.
Accordingly, a technology has been suggested with which a plurality of backup sites are provided and the redundancy of the system is ensured even when the main site stops (Japanese Patent Application Laid-open No. 2005-84953). With the conventional technology described in this publication, as indicated in paragraphs No. 0008 to 0010 thereof, a plurality of secondary storage control devices are connected to the primary storage control device. When the storage contents of the primary storage control device is updated, this updated contents is immediately transmitted to one secondary storage control device and reflected in the storage contents of this one secondary storage control device. Furthermore, the storage contents of the primary storage control device is saved as a journal data, and the other secondary storage control device appropriately reads the journal data and reflects it in its own storage contents. The one secondary storage control device produces journal data based on the data update command from the primary storage control device and saves this journal data. When the primary storage control device stops, the other secondary storage control device reads the journal data from the one secondary storage control device and updates its own storage contents.
With the technology described in the aforementioned publication, the redundancy provided by a plurality of storage control devices can be ensured even when the primary storage control device stops. Therefore, the reliability of the storage system increases. However, because one secondary storage control device has to generate the journal data each time data update is conducted, the load on the one secondary storage control device increases. Another problem is that a volume for saving the journal data in the one storage control device has to be provided and the structure becomes complex.